Hiss from the Pass Labs Balanced Zen Line Stage.

[sismik11]

Yes, that is also my experience.

 

[AndrewT]

MosFETs are known to be noisy when used in higher gain stages.
One can get away with a mosFET front end in a lower gain power amp, but probably start to notice the added noise in a higher gain power amp.

Using mosFETs in a preamp that is followed by a higher gain power amp will have similar noise to using mosFETs in a higher gain power amp.

For higher gain after your main preamp stage one should be using transistor types that are known to be lower noise. I'd suggest cascoded jFETs, or BJTs.

 

[sismik11]

Interesting. Would it be possible to substitute the mosfets with jfet in the original design? Maybe go down to +-30V.

 

[AndrewT]

You will need to look at device dissipation and find ways to keep the jFETs cool enough.

 

[Danger Mouse]

I have the same Problem.
Hissing Bosoz, but Statement "mosfet`s are the reason" could not be the only solution.

I`ve build an Aleph P clone -> silent
The Bosoz -> hiss

both build with the same mosfets

So Aleph P should hiss, too.

I think there is somithing wrong with my build, -defective parts- noisy zener or something this way.
And it is not a Cold solder Joint i`ve resoldered everything.

Will try this when i`ve time again.

And if this will not bring a solution i rip apart the Pre and build something else.

 

[AndrewT]

what gains follow the earliest mosFET stage?